Synchronous or selective removal of nitrate and Cr(VI) by montmorillonite supported sulfidized nanoscale zerovalent iron: Role of Fe(II) and S0

• Published in: Separation and purification technology Vol. 354; p. 129006
• Main Authors: Wang, Jingshu, Chen, Chen, Jeanne Huang, Jinhui, Xiao, Nan, Li, Song
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 19.02.2025
• Subjects: Cr(VI); Nitrate; Selective removal; Sulfidized nanoscale zerovalent iron; Synchronous removal; Synchronous removal; Cr(VI); Nitrate; Sulfidized nanoscale zerovalent iron; Selective removal
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2024.129006

[Display omitted] •S-nZVI@MMT at low S/Fe improved the synchronous reduction of NO3−-N and Cr(VI).•S-nZVI@MMT at high S/Fe could selectively remove Cr(VI).•The roles of Fe(II) and S0 in synchronous/selective removal were revealed.•The reactive sites varied for synchronous/selective removal of NO3−-N and Cr(VI).•Reaction pathways and products of Cr(VI) varied in different reaction processes. The reduction process of Cr(VI) and NO3−-N by sulfidized nanoscale zerovalent iron (S-nZVI) under coexistence conditions has yet to be investigated. This study innovatively confirmed that NO3−-N and Cr(VI) could be reduced synchronously or selectively by synthesizing diverse montmorillonite-supported S-nZVI (S-nZVI@MMT) to meet different remediation requirements. Concretely speaking, S-nZVI@MMT at low S/Fe could synchronously reduce NO3−-N and Cr(VI) to NH4+-N and Cr(III). S-nZVI@MMT at high S/Fe selectively removed Cr(VI). The vital roles of Fe(II) and S0 in S-nZVI@MMT were clearly revealed. Fe(II) mainly involved in the generation of Fe3O4 during the reaction at low S/Fe, while participating in the transformation of amorphous phases of Fe3O4, FeS, and FeS2 at high S/Fe. The Fe0 and converted Fe3O4 were the primary reactive sites for the synchronous removal of NO3−-N and Cr(VI) while the surface-bound Fe(II) and converted amorphous phases of Fe3O4 and FeSx determined the selective removal of Cr(VI). Meanwhile, the high contents of S0 in S-nZVI@MMT at high S/Fe mediated the generation of FeSx during the reaction and blocked the adsorption and reduction of NO3−-N which was critical for the selective removal of Cr(VI). The variations in the reactive species of S-nZVI@MMT at different S/Fe led to discrepant Cr(VI) reaction pathways. The findings provided new insights and strategies for the practical applicability of S-nZVI. Study provides a new insight into the synchronous/selective removal of Cr(VI) and NO3−-N by S-nZVI to meet the remediation requirements for different application scenarios.